1. Field of the Invention
This invention relates to a friction welding process and temperature control systems. Such structures of this type generally allow the temperature of the weld formed by friction welding to be accurately controlled such that the welding process can be more precisely controlled which, ultimately, produces repeatable good welds and desired metallurgical properties.
2. Description of the Related Art
Friction welding is quickly becoming the desired technique used to weld high temperature materials together including advanced composites. However, in order to properly perform a friction weld, the temperature at the interface between the materials must reach a suitable value but be below the melting temperature, and the weld must be cooled in a controlled manner in order to avoid producing adverse intermetallic structures in the weld which could make the weld brittle. It is well known that friction welding produces a very narrow process or heat affected zone, hereinafter, referred to as a HAZ. This occurs due to the highly localized heating at the interface of the components to be joined. In the friction welding process, the intense but short duration of mechanical energy dissipation at the material interface surfaces produced by the high strain rate deformation generates a rapid increase in temperature. Typically temperatures reach over 1000.degree. F. followed by an extremely rapid quenching action due to heat conduction into the surrounding material. This rapid heat cooldown has a tremendous influence on the microstructure generated in the narrow process zone producing a brittle martensitic type structure in certain alloys such as titanium. Therefore, a more advantageous system, then, would be presented if the cooldown of the weld could be controlled.
It is apparent from the above that there exists a need in the art for a temperature control system which measures and controls the weld temperature of a friction weld in an unobtrusive manner and, in particular, controls the weld cooldown to avoid the production of intermetallics in the weld.